Assisted reproductive technology (ART) has been a breakthrough in the treatment of infertility since the 1990s. ART options are generally provided to couples in a sequence starting from simple to more complicated techniques. Typically, the sequence is Intra-Uterine-Insemination (IUI), In-Vitro Fertilization (IVF), and Intra Cytoplasmic Sperm Injection (ICSI).
IUI is a simple procedure with less risks and ethical issues surrounding it. IUI is used in human infertility treatment by manually introducing sperms into the female reproductive tract. IUI, although less risky and complex, has shown low rates of success in ART. In comparison, IVF and ICSI have shown considerably more success than IUI. However, both IVF and ICSI are expensive techniques, thereby, reducing feasibility. Further, IVF and ICSI are associated with ethical issues.
In all three ART techniques as mentioned above, sperm count, motility, and morphology are routinely used in semen analysis to rule out male infertility and to isolate viable sperms. In the case of IUI, success rates of conception are directly related to the availability of semen sample of high sperm motility and concentration. Therefore, success rate of IUI is dependent of fertility of males. Hence, in most male infertility cases, IUI is not generally recommended. Further, for IVF and ICSI demand for isolation and processing of motile and viable sperms for infertility treatment is increasing. Sperm motility and viability depends on spermatogenesis. Studies have shown that when spermatogenesis is compromised, a great percentage of sperms in the ejaculate may show abnormalities that include membrane, mitochondrial, nuclear, and chromosomal anomalies.
In addition to isolating high motility and viability sperms from the semen sample, in ART techniques, sample preparation methods are also vital. Studies have shown that the seminal plasma may contain some components such as prostaglandins, which inhibit fertilization and pregnancy (Shivaji & Bhargava, 1987). Therefore, during sample preparation for ART seminal fluid has to be removed. Most methods of sample preparation for IUI prefer to dilute the semen with culture media and centrifuge it.
The basic technique of separating sperms of high motility is based on the conventional, “swim-up” (SU) technique, which depends on the active movement of sperms from a cell pellet into an overlaying medium; or the discontinuous density gradient (DG) centrifugation, which uses centrifugation of seminal plasma to separate cells by their density. DG centrifugation is used to separate motile spermatozoa from dead sperms, leukocytes, and the other components of the seminal plasma in cases of severe oligozoospermia, teratozoospermia or asthenozoospermia. Both these techniques separate sperms based on motility. This is because motility is important in natural conception, especially in case of IUI. After the sperm reaches the oocyte, functional properties of the sperm, such as acrosome status and DNA maturity, determine penetration of zona pellucida and fertilization of oocyte, leading to successful pregnancy.